Tightened security for the Boston Marathon, to be run April 21, includes more police and a bigger list of searchable items, officials said Monday. Last year, two homemade bombs exploded near the finish line, with devastating impact.

Officials hold a news conference regarding security measures for the upcoming Boston Marathon in Framingham, Mass., Monday, March 10, 2014. Spectators are strongly discouraged from bringing backpacks, coolers and other large items, and instead are urged to carry belongings in clear plastic bags like those being given to runners to stow their gear.

Almost one year after two homemade bombs made from pressure cookers exploded near the Boston Marathon finish line, state and marathon officials on Monday announced tightened security measures for this year's race that include a fortified police presence and a ban on baby strollers.

The new measures – the result of a seven-month review of how to keep runners and spectators safe at the April 21 race – will double the number of uniformed and plainclothes cops at the event and will add numerous items, such as backpacks and purses, to the list of articles subject to police search. Officials have also put a kibosh on unregistered runners jumping onto the 26.2-mile course to run parts of the race, citing security concerns.

Suspect Dzhokhar Tsarnaev faces 30 federal charges for his alleged role in the bombings, as well as for the fatal shooting of a campus police officer at the Massachusetts Institute of Technology, in Cambridge, Mass., three days after the attack. He has pleaded not guilty to all charges and faces a possible death sentence if convicted. His trial is expected to begin in the fall.

State officials said Monday that 3,500 police officers will be at the marathon this year, double the number patrolling last year. Plus, 100 security cameras will be added along the race course and surrounding areas, according to The Associated Press. The Tsarnaev brothers were identified after the attack with the help of security camera footage from the finish line.

Officials have also banned several more items besides the usual suspects of firearms and explosives. They include baby strollers, costumes that obscure the face, and containers that can hold more than one liter of liquid. Officials discourage marathon spectators from bringing other items that will be subject to search, including large purses, coolers, and big blankets, and advise them to ease the security process by putting their belongings in clear plastic bags, according to the Boston Athletic Association, which organizes the Boston Marathon.

"We are confident that the overall experience of runners and spectators will not be impacted, and that all will enjoy a fun, festive and family-oriented day," Kurt Schwartz, director of the Massachusetts Emergency Management Agency, told The Associated Press.

Runners will have to check their gear with marathon organizers and transfer it into plastic bags before boarding buses to the start line, according to the Boston Athletic Association. Runners will not be allowed to bring backpacks onto those buses.

In an end to marathon tradition, officials are also prohibiting unregistered runners from hopping into the race to run alongside family or friends.

"We are aware that many people want to participate in some way in this year’s Boston Marathon as a display of support,” writes the Boston Athletic Association, on its website, “but we ask that those who are not official participants to refrain from entering the course for the safety of the runners and themselves.”